Desulfurizing of sulfid ores preparatory to smelting.



1 OFFIC ARcHIBA-LnunuisiiiouD OARMIOHAELQF BRoKEN' HILL, New sou'rul" "WALES, AUSTRALIA. L

nssuitual'zme o'F su Flo ones PREPARATORYTO smegma I srncrnica'rron formingpart of Letters Patent m ma, data m 29, 1902.

' Application sue November 11,

To all whomjtmayconcerm .Be it known that I, AR'cmBALD DRUMMOND CARMIGHAEL}, metallurgist, a subject of the Kingof Great Britain, residing atthe .Royal Hotel, Argent street, Broken Hill, in the State of New South Wales, in the Commonwealth of Australia, have invented certainnew and useful Improvements in the Desulfnrizing of Sulfid Ores Preparatory to Smeltin g, of

which the following is a specification. v

This invention relates to the' treatment of sulfid ores or metallic sulfide, mattes, or metallnrgical products preparatory to smelting,

. and more particularly to the'treatment of lead snlfid ores and other metallic sulfide, such as sulfids of zinc, copper, or iron and mixtures of the same. Its object is to desulfurize and cinerate such ores or products andto change them into a condition more suit able for'the smelting process. In the processes hitherto employed such ores o'r prodf ucts have first been subjected to a prelimi nary roast in a suitable furnace, with or withwhere it has been subjected to a current of induced air for the completion of the oxidation.-

My invention consists, essentially, in disp'ensing with the preliminary roasting and in the complete desulfurization and cineration "of the sulfids in the converter in one operation. I accomplish this by mixing with the raw sulfid ore or metallurgical product a suit able proportion of calcium sulfate and by subjecting the mixture in a converter to the action of an induced current of air, starting the rea tions by means of heat,whei'eby sulfate of j the metal and calcium sufid are produced, and the calcium sulfid in its oxidation produces sufficient' heat to set iip the necessary desul- 'furizatiou reactions and to thoroughly oxidize and cinerat'e theore without loss by volatilization.

In place of calcium sulfate I may employ gypsum or sulfid of calcium where the latter can be obtained at less cost as a waste product in such as the Leblanc alkali process. Where gypsum is employed, it may be found 1901; a sure. 81,941.: (anae ia a ess before employing it in the converter.

In my invention I first intimately mix with the sulfid ore or product a definite percentage of calcium sulfate .or calcium sulfid or gypsum. The percentage required maybe from ten to thirty-five per cent, according to the grade of ore under treatment. The mixture is fed into a converter and gradually heated externally until the lower portion of the This heated mixture being continuously subjected to the induced current of air, the calcium sulfid is oxidized and converted into calcium sulfate, andthe calcium sulfate is thus regenerated for renewed use according to the following equation:

4 cas+4o=caso,, and in such exothermicchemical reaction suflicient heat is gener'atedto complete the desulfurization of the charge by the concurrent-reactions-set up by the metallic oxids desirable toisubjectit to a dehydrating proc-'- and sulfates produced by the calcium sulfate salt on fresh, or undecomposed portions of the original charge of 'ore stuff, as hereinafter described. The calcium sulfate being regenerated is free to react on a furtheredefinite portion of the undeco mposed original charge of ore stuff or metallurgical product with a si milar result as that before described, and these alternating reactions occur until near the end of the treatment. Concurrently with the sul- 'fatiziug of the metallic sulfide by the calof the induced curre'ht of air the following reactions and desulfurizing changes are effected in the charge of ore stuif as the temperature increases from the exothermic reactions and in direct proportion to the amount of the sulfate of metal formed. The first that probably occurs is that in which two molecules of the metallic sulfidreact on one molecule of the metallic sulfatewi-th. reduction to the metal metallic sulfid and sulfurous acid, as shown by the following equation in the'case o cad:

In the presence of the induced current of air which is permeating the mass the metal so formed'is oxidized and in this state reacts on a further portion of'the produced. metallic sulfid with an increased formation of metal.

and evolution of sulfurous acid according to the following equation in the case of lead:

The metal so produced in this last reaction is wholly or partially reoxidized from the oxygen of the air-current and beingfree to react on still further portions of the metallic sulfidi repeats the reaction and becomes an importaut factor in the desulfurizing of the undecouiposed portion of the charge of ore stufi. As the desulfurization proceeds and the sulfate of metal accumulates, reactions are set up between the metallic sulfid and different With three molecules of metallic sulfate to one of metallic sulfid in the case of lead according to the following equation:

At this stage of the desulfurization the temperature of the mass has reached about a maximum ,a considerable shrinkage has taken place, and the mixture has atendency to become pasty. This becomes more marked as he production of metallic oxidpred'ominates,

to the following equa and as the desired desulfurization-point is attained the mixture fuses to a mass of metallic mation of a plumbate of calcium and evolution of sulfurous acid. The mass consisting of metallic oxid and plumbate of calciumthen cools and cinerates as the exothermic action ceases and can be'readily removed to a blastfurnace for smelting for the recovery of the metals. 7

Though my invention is described more particularly with reference to lead sulfid ores containing zinc, such as are com monly known '38 the Broken Hill'sulfid's, I wish it to be clearly understood that my process may be equally applied to other classes of sulfid ores,

such as copper sulfids, &c. 7

What I claim, and desire to secure by Letters Patent of the United States, is-- 1. The process of treating mixed sulfid ores, which consists in mixing with said ores a sul+ fur compound of a metal of the alkaline earths, starting the reaction by heating the same, thereby oxidizing the sulfid and reducing the sulfur compound of the alkalimetal, passing a current of air to oxidize the reduced sulfur compound of the metal of the 'a'lkalies preparatory to acting upon a new charge of sulfid ores, substantiallyas and for the-purpose set forth.

2. The process of treating mixed sulfid ores, which consists in mixing calcium sulfate with said ores, starting the reactionby means of heat, thereby oxidizing the sulfid ores, liberating sulfurous-acid gas andv converting the calcium sulfate into calcium sulfid and oxidizing the calcium sulfid to sulfate preparatory to treating a fresh charge of sulfid ores,

substantially as and for the purpose set forth. 1 In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

' ARCHIBALD DRUMMOND CARMICHAEL. Witnesses:

CHARLES ANDREW MURPHY, CHARLES STANLEY BURGESS. 

